Heathrow Airport's director of external affairs has warned Belfast's links "could be" cut as pressure mounts on British Airways and others to replace regional routes with more valuable international flights.

Heathrow Airport's director of external affairs has warned Belfast's links "could be" cut as pressure mounts on British Airways and others to replace regional routes with more valuable international flights.

It comes as Northern Ireland peer Lord Empey warned Heathrow could ditch its Belfast slots if its expansion plans are blocked.

The Airports Commission, chaired by Sir Howard Davies, is expected to publish its final report on whether Heathrow or Gatwick should expand this summer.

But Heathrow's Nigel Milton said Belfast "could be" cut if the Airport Commission doesn't allow plans for the airport to expand.

"It could be. If Heathrow doesn't expand, the regional services from the UK are going to come under intense pressure," he told the Belfast Telegraph.

"Lord Empey's Bill is important, but our concern is different because it's not the UK Government, but the airlines' decision.

"They will be faced with this false choice. They should be doing both. We've been asked, what's more important - new routes to China or others?"

Lord Empey said: "This is what I fear most - and the Government has no power whatsoever to intervene to prevent the isolation of our major regional cities.

"In the case of Northern Ireland, we depend even more heavily on this connection because we have no rail or road alternative to the mainland."

Willie Walsh's IAG is in the process of buying Aer Lingus, which also owns British Airways. Both airlines currently fly into Belfast City Airport from Heathrow. While the group said Aer Lingus would service the Heathrow route for at another five years, no written assurances have been made over the future of the British Airways link.

"When you have a scarce resource, a commercially focused company will look to use that in any way they can," Mr Milton said.

"If it's between a 150-seat plane to Belfast or 500-seat aircraft to LA, in the same slot, which do you choose?

"They (the airlines) are forced to choose one or the other, and that's what we call it a false choice.

"Many Northern Ireland politicians have put their head above the parapet, and we need them to keep doing that over the next few weeks."

Enterprise Minister Jonathan Bell said that "the comments from Heathrow Airport highlight the importance of the Government making a quick decision in favour of expanding UK hub airport capacity".

But he did not say whether he would put into writing and bring the issue before the Assembly to seek guarantees Belfast's links will be maintained. He said: "DETI's representations to the Airport Commission emphasised the importance that any expansion of capacity at the UK hub must be of sufficient scale to provide for routes from Northern Ireland. DETI also stressed that in the absence of increased capacity at the UK hub, a long-term solution must be found which secures our essential links to the UK hub airport."

Lord Empey has said his proposed Bill will have its second reading on June 19, and he has written to Secretary of State Theresa Villiers and Regional Development Minister Danny Kennedy seeking support for the proposal.

In response to Heathrow's claims, Gatwick airport's chief executive Stewart Wingate said: “Resorting to threats of cutting routes simply demonstrates that Heathrow is losing the argument. In contrast, Gatwick is already the best-connected London airport for Northern Ireland, links that would only strengthen with expansion.

"Gatwick will also establish a £20m fund to support new air services to Gatwick from around the UK, double the amount offered by Heathrow."